Study of isospin fluctuations in Au + Au collisions at √S NN = 200GeV Tomoaki Nakamura / Kensuke Homma for the PHENIX Collaboration Hiroshima University Contents History of Centauro Search Search Strategy Observable and Analysis Method Analysis Results Summary and Future Plan

Centauro /Anti Centauro Event (Cosmic ray experiment) (Brazil-Japan collaboration in Bolivia) Y.Fujimoto and S.Hasegawa, Phys. Rep. 65, 151 (1980) (JACEE) J.J.Lord and Iwai, Paper No. 515, International Conference on High Energy Physics, Dallas (1992) O : Photon, + : Charged Particle Anti Centauro This is anomalous region assuming isospin symmetry.

List of Centauro Searches ExperimentCollaborationCM EnergySearch Region (η,φ) 1980Mt. Chacaltaya Brazil-Japan √s ≧ 1.7 TeV BalloonJACEE <η<9.0 ⊿ φ<2π 1982SPPSUA5√s=540 GeV|η|< SPPSUA1√s=540 GeV|η|< SPPSUA5√s=900 GeV|η|< TEVATRONCDF√s=1.8 TeV |η|<4.2, ⊿ φ<2π 1997TEVATRONMINIMAX√s=1.8 TeV3.4<η< SPSWA98√s=3.5 TeV (Pb+Pb)2.80<η< 3.75 ⊿ φ<π 2001RHICPHENIX√s=39.4 TeV (Run2) (Au+Au) |η| < 0.35 ⊿ φ<1/2π (×2 arm)

Disoriented Chiral Condensate (Quench Mechanism) K.Rajagopal and F.Wilczek : Nucl. Phys. B379, 395 (1993) Chiral transformation Linear sigma model quench σ π V σ π V restoration QCD vacuum DCC Chiral symmetry breaking term due to finite masses

Search Strategy If every event could contain largely deviated domains on isospin symmetry and most of domains per event could be detected within a limited detector acceptance, we would be able to discuss anomaly based on the probability distribution by the statistical treatment like: probability : P(f) fraction : f DCC (Centauro type) No DCC (binomial) However, we do not know domain information on the numbers and sizes a priory, and our detector acceptance is very limited. Therefore we need to search for rare events containing anomalous domain like cosmic ray experiments rather than statistical treatment above.

We search for a most largely deviated domain per event by looking at differences between number of charged and photon-like clusters by changing regions of interest as we do by eyes, because we don’t know what the size is and where the position is. We want to extract this region. We must do this search in several million events. Maximum deviation in an event

Observables Definition of asymmetry between number of charged tracks and neutral clusters event-by-event base as a function of subdivided eta-phi phase spaces normalized by 1 sigma of standard deviation for given multiplicity. δA I3 Domain Size Deviation Size Domain Position η,φ Domain Size and Domain Position of large deviated region can be obtained at the same time by using Multi Resolution Analysis (MRA) technique.

Multi Resolution Analysis (MRA) δAsymmetry 0 0 ① ② ① ② ① ① ① ① ② ② ② ② ①－② η,φ δAI3 : Ncharge - Nphoton Extract this region

eta (j=4)phi(j=4) C 1) projection on eta 2) projection on phi 1) projection on phi 2) projection on eta Domain C: A I3 = ~20 x 8bins ( ,  )=(3, 7) (j , j  )=(3, 2) A B Result:Correct ( ,  )=(3,7) (j ,j  )=(3,2) Result:Wrong ( ,  )=(7,1) (j ,j  )=(2,4) Example of 2D MRA

PHENIX Experiment at Run2 Using Magnetic Field-off data Charged Track (BBC Z-Vertex, Drift Chamber and Pad Chamber1) Photon-like Cluster (Electro-Magnetic Calorimeter) in each arm

Data Sample Magnetic Field-off Minimum bias 873,881 events number of charged tracks > 0 number of photon-like clusters >0 Charged Track BBC Z-Vertex, Drift Chamber and Pad Chamber1 associated straight-line track Photon-like Cluster Cluster of Electro-Magnetic Calorimeter 1) Cluster shower shape 2) Time of flight 3) Not associated with charged track Number of Charged Tracks Number of Photon-like Clusters Charged vs. Photon-like We can detect both charged tracks and photon-like clusters even below 100MeV/c.

Binomial Distribution as a Baseline Fluctuation We need to define a degree of the anomaly quantitatively with a familiar statistical language. We have also taken care of detector bias in real data. Binomial samples are generated based on hit map of real data for ~3000 events term. φ φ ηη Charged Photon-like Maximum Deviation Size (Binomial sample) (Nch, Nphoton) = (200, 100) Hit Map Without hitmap With hitmap

Maximum Deviation Size Level-by-Level ⊿ η: ⊿ φ: 2.813° 5.625° 11.25° 22.50° 45.00° [East Arm] – – – – Minimum bias 873,881 events -- Data --Binomial

[eta] [phi] # of gamma-like : 2 # of charged : 49 Event Display (East Arm) ⊿ η=0.35 ⊿ φ=0.175

Maximum Deviation Size charged/photon-like for all events Deviation size (A.U.) PHENIX magnetic field-off minimum bias Au+Au 200 GeV data (873,881 events) East Arm [Uncorrected] Binomial sample with dead channel map (Same statistics and same multiplicity as real data)

Summary and Future Plan We have demonstrated two dimensional multi-resolution analysis on the asymmetry between the number of charged tracks and γ-like clusters in the η-φ phase space for the PHENIX Au+Au 200GeV data. Set a reasonable significance level to define the degree of anomaly based on the physical models with normal fluctuations. Count the anomalous events above the significance level. For those events above the significance level, we will analyze the signal to background ratio (S/√B) as a function of centrality. Discuss the event characters of those events, if they are found.

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Multi Resolution Analysis (MRA) Wavelet function Scaling function Level j-1 : 2 j-1 binsLevel j : 2 j bins φ(2x) = 1/√2 {φ(x) + ψ(x) } φ(2x-1) = 1/√2 {φ(x) - ψ(x) } -0.7 ＝ (－)(－) (＋)(＋) 0.7 φ(x) 0.7 ψ(x) x x 1 1 φ(2x-1) x 1 1 φ(2x) x -0.7 Total number of bins is 2 j Level j correspond to resolution level

Signal Decomposition j : resolution level k : k-th bin in pseudo rapidity Cjk : coefficients of φ Djk : coefficients of ψ Signal φψ kk j=4 j=3 j=2 j=1 j=0 Cjk Djk 1/2 j → Domain Size k → Phase Space Position Djk → Deviation Size Look for Djkmax in a event

Window Shift Method Shift the start bin at each resolution level. Find djk max among all of levels. This can determine the level (domain size) with the largest deviation size. should appear here ! A symmetric structure appears in wrong level djk is lower